Semiconductor Microwave Amplitude and Phase Modulator

摘要

Experiments on the amplitude modulator were extended into the uhf range. Typical measurements on experimental epitaxial silicon diodes yielded modulation indices of approximately 50 percent at 220 Mc/s and approximately 15 percent at 400 Mc/s. This decrease in modulation depth with increasing modulation frequency appears to be due to the frequency sensitivity of the wafer in which the diode is mounted. A new test structure has been designed which will enable a more accurate and reliable measurement of the equivalent circuit parameters of the PIN diode at 70 Gc/s. This unit is presently being fabricated. An experimental method was established for tuning the varactor phase shifter for maximum phase shift. This condition of tuning does not correspond to minimum insertion loss. In the 70-Gc/s hybrid ring configuration 50 degrees of phase shift was obtained with a 3.4 dB insertion loss. A method for coating the surface of the point-contact GaAs varactors with a thin epoxy film was developed in an effort to improve varactor stability. Initial tests on fourteen diodes treated in this manner show promising results. (Author)